IKSEMICON IL2575-15D2

TECHNICAL DATA
1.0 A, 15 V, Step-Down
Switching Regulator
The IL2575 series of regulators are monolithic integrated
circuits ideally suited for easy and convenient design of a step–
down switching regulator (buck converter). All circuits of this series
are capable of driving a 1.0 A load with excellent line and load
regulation. These devices are available in fixed output voltages of
3.3 V, 5.0 V, 12 V, 15 V, and an adjustable output version.
These regulators were designed to minimize the number of
external components to simplify the power supply design. Standard
series of inductors optimized for use with the IL2575 are offered by
several different inductor manufacturers. Since the IL2575
converter is a switch–mode power supply, its efficiency is
significantly higher in comparison with popular three–terminal
linear regulators, especially with higher input voltages. In many
cases, the power dissipated is so low that no heatsink is required
or its size could be reduced dramatically.
A standard series of inductors optimized for use with the
IL2575 are available from several different manufacturers. This
feature greatly simplifies the design of switch–mode power
supplies. The IL2575 features include a guaranteed ±4% tolerance
on output voltage within specified input voltages and output load
conditions, and ±10% on the oscillator frequency (±2% over 0°C to
125°C). External shutdown is included, featuring 80 ㎂ (typical)
standby current. The output switch includes cycle–by–cycle current
limiting, as well as thermal shutdown for full protection under fault
conditions.
IL2575-xx
TO-220-5L
TO-220-5L
TO-263-5L
ORDERING INFORMATION
IL2575Q
IL2575S
IL2575D2
TO-220-5L
TO-220-5L
TO-263-5L
TA = -40° to 125° C for all packages
Features
•
•
•
•
•
•
•
•
•
•
3.3 V, 5.0 V, 12 V, 15 V, and Adjustable Output Versions
Adjustable Version Output Voltage Range, 1.23 to 37 V ±4%
Maximum Over Line and Load Conditions
Guaranteed 1.0 A Output Current
Wide Input Voltage Range
Requires Only 4 External Components
52 kHz Fixed Frequency Internal Oscillator
TTL Shutdown Capability, Low Power Standby Mode
High Efficiency
Uses Readily Available Standard Inductors
Thermal Shutdown and Current Limit Protection
Pin connections
1. Vin
2. Output
3. Ground
4. Feedback
5. ON/OFF
Applications
•
•
•
•
•
•
Simple High–Efficiency Step–Down (Buck) Regulator
Efficient Pre–Regulator for Linear Regulators
On–Card Switching Regulators
Positive to Negative Converter (Buck–Boost)
Negative Step–Up Converters
Power Supply for Battery Chargers
Rev. 00
IL2575-xx
Typical Application (Fixed Output Voltage Versions)
Representative Block Diagram and Typical Application
This device contains 162 active transistors.
Figure 1. Block Diagram and Typical Application
ABSOLUTE MAXIMUM RATINGS
(Absolute Maximum Ratings indicate limits beyond which damage to the device may occur.)
Rating
Maximum Supply Voltage
ON/OFF Pin Input Voltage
Output Voltage to Ground (Steady–State)
Power Dissipation
TO–220, 5–Lead
Thermal Resistance, Junction–to–Ambient
Thermal Resistance, Junction–to–Case
D2PAK
Thermal Resistance, Junction–to–Ambient
Thermal Resistance, Junction–to–Case
Storage Temperature Range
Minimum ESD Rating (Human Body Model:
C = 100 pF, R = 1.5 kΩ)
Lead Temperature (Soldering, 10 seconds)
Maximum Junction Temperature
Symbol
Value
Unit
Vin
–
–
45
–0.3 V ≤V ≤ +Vin
–1.0
V
V
V
PD
RθJA
RθJC
PD
RθJA
RθJC
Tstg
–
Internally Limited
65
5.0
Internally Limited
70
5.0
–65 to +150
2.0
W
°C/W
°C/W
W
°C/W
°C/W
°C
kV
–
TJ
260
150
°C
°C
Rev. 00
IL2575-xx
OPERATING RATINGS
(Operating Ratings indicate conditions for which the device is intended to be functional, but do not guarantee specific
performance limits. For guaranteed specifications and test conditions, see the Electrical Characteristics.)
Rating
Operating Junction Temperature Range
Supply Voltage
Symbol
TJ
Vin
Value
–40 to +125
40
Unit
°C
V
SYSTEM PARAMETERS [Note 1]
ELECTRICAL CHARACTERISTICS
(Unless otherwise specified, Vin = 12 V for the 3.3 V, 5.0 V, and Adjustable version, Vin = 25 V for the 12 V version, and Vin = 30 V for
the 15 V version. ILoad = 500 mA, TJ = 25°C, for min/max values TJ is the operating junction temperature range that applies [Note 2],
unless otherwise noted.)
Characteristics
IL2575–3.3 ([Note 1] Test Circuit Figure 14)
Output Voltage (Vin=12V, ILoad=0.2A, Tj=25°C)
Output Voltage (4.75V ≤Vin ≤40V, 0.2A ≤ILoad ≤1.0A)
TJ = 25°C
TJ = –40 to +125°C
Efficiency (Vin = 12V, ILoad = 1.0A)
IL2575–5 [Note 1]
Output Voltage (Vin=12V, ILoad=0.2A, Tj=25°C)
Output Voltage (8.0V ≤Vin ≤40V, 0.2A ≤ILoad ≤1.0A)
TJ = 25°C
TJ = –40 to +125°C
Efficiency (Vin = 12 V, ILoad = 1.0 A)
IL2575–12 [Note 1]
Output Voltage (Vin=25V, ILoad=0.2A, Tj=25°C)
Output Voltage (15.0V ≤Vin ≤40V, 0.2A ≤ILoad ≤1.0A)
TJ = 25°C
TJ = –40 to +125°C
Efficiency (Vin = 15V, ILoad = 1.0A)
IL2575–15 [Note 1]
Output Voltage (Vin=30V, ILoad=0.2A, Tj=25°C)
Output Voltage (18V ≤Vin ≤40V, 0.2A ≤ILoad ≤1.0A)
TJ = 25°C
TJ = –40 to +125°C
Efficiency (Vin = 12V, ILoad = 1.0A)
IL2575 ADJUSTABLE VERSION [Note 1]
Feedback Voltage (Vin=12V, ILoad =0.2A, Vout = 5.0V,
TJ=25°C)
Feedback Voltage (8.0V ≤Vin ≤ 40V, 0.2A ≤ILoad ≤1.0A,
Vout=5.0V)
TJ = 25°C
TJ = –40 to +125°C
Efficiency (Vin = 12V, ILoad = 1.0A, Vout = 5.0V)
Symbol
Vout
Vout
Min
Max
Unit
3.234
3.366
V
V
3.168
3.135
3.432
3.465
η
65
-
%
Vout
Vout
4.9
5.1
V
V
4.8
4.75
5.2
5.25
η
67
-
%
Vout
Vout
11.76
12.24
V
V
11.52
11.4
12.48
12.6
η
78
-
%
Vout
Vout
14.7
15.3
V
V
14.4
14.25
15.6
15.75
η
78
-
%
Vout
1.217
1.243
V
Vout
η
V
1.193
1.18
67
1.267
1.28
-
%
1. External components such as the catch diode, inductor, input and output capacitors can affect switching regulator system
performance.
When the IL2575 is used as shown in the test circuit 14, system performance will be as shown in system parameters section .
2. Tested junction temperature range for the IL2575: Tlow = –40°C Thigh = +125°C
Rev. 00
IL2575-xx
DEVICE PARAMETERS
ELECTRICAL CHARACTERISTICS
(Unless otherwise specified, Vin = 12 V for the 3.3 V, 5.0 V, and Adjustable version, Vin = 25 V
for the 12 V version, and Vin = 30 V for the 15 V version. ILoad = 500 mA, TJ = 25°C, for min/max values TJ is the
operating junction temperature range that applies [Note 2], unless otherwise noted.)
Characteristics
ALL OUTPUT VOLTAGE VERSIONS
Feedback Bias Current (Vout = 5.0 V [Adjustable Version
Only])
TJ = 25°C
TJ = –40 to +125°C
Oscillator Frequency [Note 3]
TJ = 25°C
TJ = –40 to +125°C
Saturation Voltage (Iout = 1.0 A [Note 4])
TJ = 25°C
TJ = –40 to +125°C
Max Duty Cycle (“on”) [Note 5]
Current Limit (Peak Current [Notes 3 and 4])
TJ = 25°C
TJ = –40 to +125°C
Output Leakage Current [Notes 6 and 7], TJ = 25°C
Output = 0 V
Output = –1.0 V
Quiescent Current [Note 6]
TJ = 25°C
TJ = –40 to +125°C
Standby Quiescent Current (ON/OFF Pin = 5.0 V (“off”))
TJ = 25°C
ON/OFF Pin Logic Input Level
Vout = 0 V
TJ = 25°C
TJ = –40 to +125°C
Vout = Nominal Output Voltage
TJ = 25°C
TJ = –40 to +125°C
ON/OFF Pin Input Current
ON/OFF Pin = 5.0 V (“off”), TJ = 25°C
ON/OFF Pin = 0 V (“on”), TJ = 25°C
Symbol
Min
Max
Ib
fosc
Vsat
DC
ICL
IL
IQ
Unit
nA
–
–
100
500
–
42
–
63
–
–
93
1.8
2.0
–
4.2
3.5
6.9
7.5
–
–
2.0
30
–
–
10
11
–
200
kHz
V
%
,A
mA
mA
Istby
uA
V
VIH
VIL
2.2
2.4
–
–
–
–
1.0
0.8
–
–
30
10
uA
IIH
IIL
3. The oscillator frequency reduces to approximately 18 kHz in the event of an output short or an overload which causes the regulated
output voltage to drop approximately 40% from the nominal output voltage. This self protection feature lowers the average dissipation of
the IC by lowering the minimum duty cycle from 5% down to approximately 2%.
4. Output (Pin 2) sourcing current. No diode, inductor or capacitor connected to output pin.
5. Feedback (Pin 4) removed from output and connected to 0 V.
6. Feedback (Pin 4) removed from output and connected to +12 V for the Adjustable, 3.3 V, and 5.0 V versions, and +25 V for the 12 V
and 15 V versions, to force the output transistor “off”.
7. Vin = 40 V.
Rev. 00
IL2575-xx
TYPICAL PERFORMANCE CHARACTERISTICS (Circuit of Figure 14)
Figure 2. Normalized Output Voltage
Figure 3. Line Regulation
Figure 4. Switch Saturation Voltage
Figure 5. Current Limit
Figure 6. Dropout Voltage
Figure 7. Quiescent Current
Rev. 00
IL2575-xx
Figure 8. Standby Quiescent Current
Figure 9. Standby Quiescent Current
Figure 10. Oscillator Frequency
Figure 11. Feedback Pin Current
Figure 12. Switching Waveforms
Figure 13. Load Transient Response
Rev. 00
IL2575-xx
5.0 Output Voltage Versions
Adjustable Output Voltage Versions
Figure 14. Typical Test Circuits
PCB LAYOUT GUIDELINES
As in any switching regulator, the layout of the printed circuit board is very important. Rapidly switching
currents associated with wiring inductance, stray capacitance and parasitic inductance of the printed circuit
board traces can generate voltage transients which can generate electromagnetic interferences (EMI) and
affect the desired operation. As indicated in the Figure 14, to minimize inductance and ground loops, the
length of the leads indicated by heavy lines should be kept as short as possible. For best results, single–
point grounding (as indicated) or ground plane construction should be used.
On the other hand, the PCB area connected to the Pin 2 (emitter of the internal switch) of the IL2575
should be kept to a minimum in order to minimize coupling to sensitive circuitry. Another sensitive part of the
circuit is the feedback. It is important to keep the sensitive feedback wiring short. To assure this, physically
locate the programming resistors near to the regulator, when using the adjustable version of the IL2575
regulator.
Rev. 00
IL2575-xx
APPLICATION INFORMATION
INVERTING REGULATOR
Figure 15. Inverting Buck–Boost Regulator Using the
IL2575–12 Develops –12 V @ 0.35 A
An inverting buck–boost regulator using the IL2575–12 is shown in Figure 15. This circuit converts a
positive input voltage to a negative output voltage with a common ground by bootstrapping the regulators
ground to the negative output voltage. By grounding the feedback pin, the regulator senses the inverted
output voltage and regulates it.
In this example the IL2575–12 is used to generate a –12 V output. The maximum input voltage in this
case cannot exceed +28 V because the maximum voltage appearing across the regulator is the absolute
sum of the input and output voltages and this must be limited to a maximum of 40 V.
This circuit configuration is able to deliver approximately 0.35 A to the output when the input voltage is
12 V or higher. At lighter loads the minimum input voltage required drops to approximately 4.7 V, because
the buck–boost regulator topology can produce an output voltage that, in its absolute value, is either greater
or less than the input voltage.
Since the switch currents in this buck–boost configuration are higher than in the standard buck converter
topology, the available output current is lower.
This type of buck–boost inverting regulator can also require a larger amount of startup input current,
even for light loads. This may overload an input power source with a current limit less than 1.5 A.
Such an amount of input startup current is needed for at least 2.0 ms or more. The actual time depends
on the output voltage and size of the output capacitor.
Because of the relatively high startup currents required by this inverting regulator topology, the use of a
delayed startup or an undervoltage lockout circuit is recommended.
Using a delayed startup arrangement, the input capacitor can charge up to a higher voltage before the
switch–mode regulator begins to operate.
The high input current needed for startup is now partially supplied by the input capacitor Cin.
Design Recommendations:
The inverting regulator operates in a different manner than the buck converter and so a different design
procedure has to be used to select the inductor L1 or the output capacitor Cout.
The output capacitor values must be larger than is normally required for buck converter designs. Low
input voltages or high output currents require a large value output capacitor (in the range of thousands of uF).
The recommended range of inductor values for the inverting converter design is between 68 uH and
220 uH. To select an inductor with an appropriate current rating, the inductor peak current has to be
calculated.
The following formula is used to obtain the peak inductor current:
Under normal continuous inductor current operating conditions, the worst case occurs when Vin is
minimal. Note that the voltage appearing across the regulator is the absolute sum of the input and output
voltage, and must not exceed 40 V.
Rev. 00
IL2575-xx
Figure 16. Inverting Buck–Boost
Regulator with Delayed Startup
It has been already mentioned above, that in some situations, the delayed startup or the undervoltage
lockout features could be very useful. A delayed startup circuit applied to a buck–boost converter is shown in
Figure 16.
Figure 22 in the “Undervoltage Lockout” section describes an undervoltage lockout feature for the same
converter topology.
NOTE: This picture does not show the complete circuit.
Figure 17. Inverting Buck–Boost Regulator Shut Down
Circuit Using an Optocoupler
With the inverting configuration, the use of the ON/OFF pin requires some level shifting techniques.
This is caused by the fact, that the ground pin of the converter IC is no longer at ground. Now, the ON/OFF
pin threshold voltage (1.4 V approximately) has to be related to the negative output voltage level. There are
many different possible shut down methods, two of them are shown in Figures 17 and 18.
Rev. 00
IL2575-xx
NOTE: This picture does not show the complete circuit.
Figure 18. Inverting Buck–Boost Regulator Shut Down
Circuit Using a PNP Transistor
Negative Boost Regulator
This example is a variation of the buck–boost topology and is called a negative boost regulator. This
regulator experiences relatively high switch current, especially at low input voltages. The internal switch
current limiting results in lower output load current capability.
The circuit in Figure 19 shows the negative boost configuration. The input voltage in this application
ranges from –5.0 V to –12 V and provides a regulated –12 V output.
If the input voltage is greater than –12 V, the output will rise above –12 V accordingly, but will not
damage the regulator.
Figure 19. Negative Boost Regulator
Design Recommendations:
The same design rules as for the previous inverting buck–boost converter can be applied. The output
capacitor Cout must be chosen larger than would be required for a standard buck converter. Low input
voltages or high output currents require a large value output capacitor (in the range of thousands of uF). The
recommended range of inductor values for the negative boost regulator is the same as for inverting
converter design.
Another important point is that these negative boost converters cannot provide current limiting load
protection in the event of a short in the output so some other means, such as a fuse, may be necessary to
provide the load protection.
Rev. 00
IL2575-xx
Delayed Startup
There are some applications, like the inverting regulator already mentioned above, which require a
higher amount of startup current. In such cases, if the input power source is limited, this delayed startup
feature becomes very useful. To provide a time delay between the time the input voltage is applied and the
time when the output voltage comes up, the circuit in Figure 20 can be used. As the input voltage is applied,
the capacitor C1 charges up, and the voltage across the resistor R2 falls down. When the voltage on the
ON/OFF pin falls below the threshold value 1.4 V, the regulator starts up. Resistor R1 is included to limit the
maximum voltage applied to the ON/OFF pin, reduces the power supply noise sensitivity, and also limits the
capacitor C1 discharge current, but its use is not mandatory.
When a high 50 Hz or 60 Hz (100 Hz or 120 Hz respectively) ripple voltage exists, a long delay time
can cause some problems by coupling the ripple into the ON/OFF pin, the regulator could be switched
periodically on and off with the line (or double) frequency.
NOTE: This picture does not show the complete circuit.
Figure 20. Delayed Startup Circuitry
Undervoltage Lockout
Some applications require the regulator to remain off until the input voltage reaches a certain threshold
level. Figure 21 shows an undervoltage lockout circuit applied to a buck regulator. A version of this circuit for
buck–boost converter is shown in Figure 22. Resistor R3 pulls the ON/OFF pin high and keeps the regulator
off until the input voltage reaches a predetermined threshold level, which is determined by the following
expression:
NOTE: This picture does not show the complete circuit.
Figure 21. Undervoltage Lockout Circuit for
Buck Converter
Rev. 00
IL2575-xx
NOTE: This picture does not show the complete circuit.
Figure 22. Undervoltage Lockout Circuit for
Buck–Boost Converter
Figure 23. Adjustable Power Supply with Low Ripple Voltage
Figure 24. D2PAK Thermal Resistance and Maximum
Power Dissipation versus P.C.B. Copper Length
`
Rev. 00
IL2575-xx
THE IL2575–5.0 STEP–DOWN VOLTAGE REGULATOR WITH 5.0 V @ 1.0 A OUTPUT POWER
CAPABILITY. TYPICAL APPLICATION WITH THROUGH–HOLE PC BOARD LAYOUT
Figure 25. Schematic Diagram of the IL2575–5.0 Step–Down Converter
NOTE: Not to scale.
NOTE: Not to scale.
Figure 26. Printed Circuit Board
Component Side
Figure 27. Printed Circuit Board
Copper Side
Rev. 00
IL2575-xx
THE IL2575–ADJ STEP–DOWN VOLTAGE REGULATOR WITH 8.0 V @ 1.0 A OUTPUT POWER
CAPABILITY. TYPICAL APPLICATION WITH THROUGH–HOLE PC BOARD LAYOUT
Figure 28. Schematic Diagram of the 8.0 V @ 1.0 V Step–Down Converter Using the IL2575–Adj
(An additional LC filter is included to achieve low output ripple voltage)
NOTE: Not to scale.
NOTE: Not to scale.
Figure 29. PC Board Component Side
Figure 30. PC Board Copper Side
Rev. 00
IL2575-xx
TO-220-5L
Rev. 00
IL2575-xx
TO-220-5L (Bent Staggered)
Rev. 00
IL2575-xx
TO-263-5L
Rev. 00